An apparatus of the generic type known from U.S. Pat. No. 3,976,414 has a nozzle ring that is adjustable in relation to the injection head in the direction of its central longitudinal axis by means of a threaded sleeve formed in one piece with it. Thus the width of the nozzle is set and consequently the wall thickness of an extrusion-molded hose of thermally plastic material is modified. In an embodiment of the apparatus for manufacturing plastic compound pipes with two channels being provided, each opening into a nozzle, each nozzle is provided with such a component adjustable in the direction of the central longitudinal axis.
In a further apparatus of the generic type known from U.S. Pat. No. 4,789,327 a jacket pipe surrounding the channel is provided on the latter's outside and adjacent to the nozzle with a thread on to which a flanged ring can be screwed. A nozzle ring is attachable to this flanged ring by means of screws. The width of the nozzle can be set by rotation of the flanged ring. The jacket pipe is radially adjustable at its end opposite the nozzle by means of adjusting screws extending radially in relation to the central longitudinal axis.